Resistor construction and insulator



Jan. 9, 1951 A. P. slEKLucKl ETAL REsIsToR CONSTRUCTION AND INsuLAToR 2 Sheets-Sheet l Filed Sept. 23, 1948 INVENTORS ALFRED P SIE/{LUCK} BY EDWARD E. KRKHAM /JT'OHNY Jan. 9, 1951 v A. P. slEKLUcKI ErAL 2,537,796

REsIsToR CONSTRUCTION AND INSULATOR Filed Sept. 23, 1948 2 Sheets-Sheet 2 i 22 g 36 i /8 el 22 ufl Z/ 1Q INVENTORS ATTORNEY Patented Jan. 9, 1951 RESISTOR CONSTRUCTION AND IlSISULA'IOR Alfred Sieklucki, Hartford, and Edward E.

Kirkharn, Manchester, Conn.,v assignors to Fed- `eralElectric.Products Company, Newark, N. J.,

.-a corporation lihtnplication.September 23, 1948,'Serial No. 50,824

. 20 Claims. 1

i'I'fhe: presentinventionv relates -to resistors and =morepa-rticularly to resistors of the type used, in

"connection with velectric inotor controls and start- 1 2ers .electric furnaces iand ovens, electrical heating units, etc.

:Due tothe fact 4thatfresistance elements under- Xga-alternate.heating and cooling innormal-operation, -rsaid :elements are subject to sagging :while heatedeandeto excessive vtensionvvhile cool- J'zing .or :When-theyfare-fcold. It'is therefore one frof the objects Yof the-.present invention to provide'improvedsupporting means for the resistance elements toyproperly `support 'the latter, without .fsaggingeunder lmaximum heat conditions there- :of-,wand to .prevent excessive stresses-WhenV the resistance elements-contract upon cooling.

Pursuant .to another .obj ect ofn the invention,

thesupporting means. comprise a plurality of insulators -whichfare so` constructed that 4they 4-may Ybe relatively ...arranged .for supporting resistance-elements of different Widths in a comparativelywiderangeof Widths of resistor elements.

According .to another objectof..the invention,

vthe yinsulators ,are .so constructed that they are 1 free .of undercut Hor other contoured portions which wouldfinterfereswiththe production thereofby a simple andinexpensive molding process. ."Another object ofthe invention is 'toprovide .a resistorV construction. made of parts whichV are .-soV constructed that they may be easily. manufacture'dl and assembled.

Another object of the invention is the-provsion of a resistor constructioninrvvhich lthe end terminals may be supportedby Ithe insulators, which maybe `positioned,selectively at any-*point along the' length of the resistance element, and which may beplaced in position or have their j positions altered yWithout requiring disassembly "ofthe resistance element and the supportingvv means.

A' further object is generally to provide a -re- 'sister' which `is compact, rugged andwdurable,

."and which 'issimple -in yconstruction `-and compa'r'atively"inexpensive to= manufacture.

'The above `andotherobjects ofi-the invention,

V'Aobjeetsv ancillaryftheretogand-ithe above mentioned andother featuresA andadvantages "of the In thefdratvings: ini-gsi israfplanzviewnffiaar-esist9rn1rhe iyig the? .present invention, -parts Kbroken Iavvay for the purpose `of illustration;

:FfigfZ is a-sidefview of thevresistor shown in `#Fig-1;

Fig. 3 isa plan view of one of the :insulators of the supporting means;

VFiga 4 is a View partly inend elevation and-partlyinsectionion the line 4 4- of Fig. 1;

-F-ig. 5 is -asectional viewon .the line. 5-.5 :of

3:10 Figi.v l;

-.Figs. v6 and 7 are side views of a pairoffterminal fmembers, respectively.

Referring now to the drawings in detail, the resistor lli-fas. illustrated, .comprises` a Aplurality 15 of units .assembled together,..as ,hereinafter more particularly described, but it willbe understood that'the resistor -may.consist of .only one-unit. The unit includes a resistanceA element l2 .and `its individual supportingemeans.

r2o In the illustratedform of the resistor .IIL the xresistance elementy l2: is of serpentine .form,k hav- Yingfa series ofreexed end portions .Ul at itsop- `positelongitudinal sides, i. .e., at lthe lOpposite -ends yofthe lseries.of...transverse parts l5. Thus, 25zfor example, when element v,l2 Vis formed .of a Y.sheet metalstrip, the latter- ,is folded back .and yforth in;zig zag fashion, along itslength in a vvellfunolerstood manner. It is to beunderstood, ,-hovveverythat the invention is not limited tothe 3o wise-of a. resistance element formed of sheetmetal, .since l the features of =the .present invention Ymay `beutilizecil in connection with resistance elements of othertypes. .The resistance element I2. is prefv .erably-anon-oxidizing,r heat resisting sheet metal `35 strip such as Nichrome.

The resistance. element is mounted in and supported by .insulators i6, Aeach vof said insulators ...beingof the saine. construction andsize andpreferably formed of porcelain. Saidinsulator Vit is 4o=1noldedintheform of a yblockhaving a series. of

. integral projectingportions 1,8 which. are disposed zinspacedrelation,longitudinally of ythe block adjacent the inner side 2l thereof. As best shown u by. Figs. land V5, the .projections |18 are posi- ,345 tionedat theiadjacentreflexed portions lll, ,re-

k.spectively, of the resistanceelernent l,2,vat the inner .sides of `said reflexed, portions, respectively. Thefinsulators Itoare comparatively short so as sto minimize the possibilityof cracking` and Warp- -V-J fing thereof, and for this reasonth'ere are aplusralityof these insulators alongthelength of the r u nit. ylt,vvil1.be observed that vthe insulators i6 are arranged in pairs atneachrlongitudinal side i of the resistance element, the,,insulatorsv of Veach frgpaintat eah. longituclinal side` of r the Vresistance element being in opposed spaced relation as illustrated in Fig. 5 and also in Fig. 4, so that the projections I8 of each pair or insulators IS overlap the adjacent reilexed portions I4 of the resistance element I2. The insulators It are also provided with a longitudinally extending groove 20, with a pair of recesses 22 and with a series of spaced transverse grooves 24, having the respective functions which will presently be described.

The insulators I5 are held in position in the above described relation to resistance element I2 by upper and lower longitudinal members, here shown as bars 25 and 28, respectively, there being two upper bars 26, one at each longitudinal side of the unit, and two lower bars 28 one at each longitudinal side of the unit. As clearly shown in the drawings, these bars are received in the longitudinal grooves 28 of the insulators I6, the lower bars 28 supporting the lower insulators IG of each unit. Said bars extend for the full length of the resistor unit and have. their opposite ends, connected to each other by cross members or brackets 29 to which the adjacent ends of said bars are releasably secured in any suitable way, preferably by screws Cross members 29, at each end of the unit are held in vertically spaced relation by rigid bars or rods 32 to which said cross members may be secured in any suitable way, for example, by being riveted thereto as indicated at 34. It will be understood that the vertical distance between cross members 29 depends upon the width of the resistance element I2. Accordingly, it will be understood that the insulators i6 of the same size may be used for resistance elements I2 of different widths, since, bars 26 and 28 may be secured in the required spaced relation depending upon the width of the resistance element l2 which is to be provided in the resistor unit.

It will be noted that the lower bars 28 of the upper resistor unit constitute the upper bars of the adjacent lower resistance unit, as is clearly evident from an inspection of Figs. 2, 4 and 5, the lower bars of said last mentioned resistance unit being indicated at 28a in Figs. 2 and 5. It will be noted that bars 2li and 28 and 28a are identical in construction and are interchangeable, and that each bar is wide enough to project into two grooves 28 of adjacent insulators I6, as is clearly apparent from an inspection of Figs. 2. 4 and 5. In this connection, it will be observed that when a plurality of resistor units are assembled together, the lower insulators of one unit are disposed adjacent to the upper insulators of the lower adjacent resistance unit. Thus the resistor units may be disposed in staclzed relation, in compact fashion without however interfering with the free flow of air around the resistance elements. It will be noted that the bar which is disposed between adjacent resistor units, in this case, bar 22 also constitutes means to space the resistance elements of adjacent units from each other.

The opposed insulators of each pair, at each side of the resistor unit, are held in predetermined spaced relation against movement toward each other by spacing members 35. the ends of which are received in the recesses 22 of the opposed confronting insulators. As best shown in Figs. 2 and 5, spacing members 36 are su'liciently long to provide clearance between the resistance element I2 and the opposed insulators of each pair, at each side of the resistor unit. so that the resistance element is free to expand when heated. Also, the spacebetween the insulators at the opposite sides of the resistance element7 i. e., laterally viewing Figs. 1 and 4, is slightly greater than the distance between the reilexed end portions I4 at one longitudinal side of the resistance element and the reflexed portions 44 at the opposite longitudinal side of the resistance element, as clearly illustrated in Fig. 1, so that in the unheated condition of the resistance element, when the latter is in its normally contracted condition, there is substantially no pressure or stress on said resistance element in said lateral direction.

Referring to the terminals 38 for the resistance element, each of the latter comprises the companion terminal members 40 and 42 which are supported in the above mentioned grooves 24 of the insulators I6. The companion terminal members 40 and 42 may be positioned anywhere along the length of the resistance element I2, the series of spaced grooves 24 being provided for this purpose. Said companion terminal members 4E and 42 are disposed at opposite sides of a transversely extending portion I5 of the resistance element I2, as illustrated in Fig. 1, said companion terminal members beingl tightly clamped against said transverse portion of the resistance element by the screws 44. As clearly shown in Fig. 4, the outer end portions 4S and 48 or" terminal members 40 and 42, respectively, extend in opposite directions and are of suflicient length to project beyond the upper and lower edges, respectively, of the resistance element I2 for securement of the companion terminal members to each other in clamping relation to said resistance element by said screws 44. Further it will lbe noted that the companion members 40 and 42 are of the same configuration so that either oi said elements may be placed at either longitudinal side of the resistor unit at which the terminal-wire fastening screw 56 is provided, the outer ends 58 of said companion terminal members having openingl 52 for the shank of said terminal screw. Further it will be observed that each terminal member has a reversely curved formation which includes the outer end portion 46 and 48 and the inner end portion 46a and 48a, respectively. By reason of this construction, each terminal member may be insert-` ed between the confronting opposed upper and lower insulators of each pair, at either side of the resistor assembly, while said insulators are in their assembled positions, shown in Figs. 1, 2 and 4, it being unnecessary to release any of the bars 25 or 28, or 28a in order to mount the terminal members 48 and 42 in the desired position, selectively, along the length of the resistance element I2. It will be understood, of course, that as clearly shown in the drawings the grooves 24 for the terminals 33 in one insulator of each pair are in Vertical registry with the corresponding g-rooves of the companion insulator of the pair at each side of the resistor unit. As hereinbefore indicated, terminal members 40 and 42 are of the same formation and are identical in all respects except that the openings 54 of terminal member 4D are not screw threaded, while the openings 56 of the companion terminal member 42 are screw threaded for screw threaded engagement by the screw fastening, openings 54 being slightly larger than the Shanks of said screws. Thus, the companion terminal members 40 and 42 are reversible with respect to each other in fastening them to the resistance element.

In the drawings, each resistor unit is shown gas; comprisingr two` upper :and two lower insulaters arranged. inend'to, endV -relationatffeach `side of the;v unit. .It-Will lbe understoodthatfwhen ,the `resistance.elementtlz is.; longer .than in the illustratedzunit, :additional :insulators .arnay be easily assembledV inv end to rend relation, bars 26ffandrl28 for'fone unit, rand bars A28 and128af-for the next unit, when provided; being ofV c0rrespondingly increased lengt-h. In'r other: words,

the-unitmay vbe of any.v length, theionly reduirement` l being` a .proportionate number, `of l the re1- atively shortinsulators: I'i'longitudinally. ofthe holding bars, according ttoftheslength oifthere- .'.sistance element-12. Onf the :other-:hand when the resistance element v .i121zisl wider than; that4 'i1- lustrated, it is only necessary'to propontionately espace'A the adjacent-cross mernberssZf'longitudinally of lthe vertical; spacing rods 32. It

willbe observed that all of the projections, grooves and' recesses of Iinsulator I6 lextend `depthwise -in the same direction,y i. e., Yini thefdivrectionr running between two vopposite sides of "thexinsulatorf block, V'thus enabling' the insulator to lbefmoldedcomplete byra simple molding :operation. Also, .it fwill be A-noted 1that1-the insulators :l Stare devoid of anyV undercut= or other contouredv -formations' which. Awould `complicate the-"molding thereon Thus, .a single .die may be used'toisproduce' allnf the necessary `insulators sin: a wide `range. ofwidths, Llengths andfthicknesses :of resistance elements.

`Whi1e1we have shown `and described-the preferrednembodiment of our-'invention it will vbe 'understoodl that various changes in the details of'fco'nstruc'tion and in the form and arrangementrof' parts-:may beV made Without` departing from'the underlyingide'a or 'principles of our inventiony Within "the scope of' the appended claims.-

Having thus describedour-invention, what we claimeand desire to .secure by Letters Patent,4 is: l. A resistor comprising a resistance. element having va series-of reexedportions alongthe lengththereof at its opposite longitudinal; sides,

a plurality of 'pairs of insulators 'for mounting said resistance element, the `companion insu- `latorsof Vone of saidy pairs of insulators being positioned in` opposed confronting relation, the

vreiiefsed portionsof `saidrelement at' one of said longitudinal sides thereof being disposedbetween the-confrontingsurfaces of said|` one pair Offinsulators, the companion insulators of' another of saidpairs of linsulators being positionedin opposed-Y-relation, the 'reflexed portions of Usaid. element at the oppositelongitudinalfside thereof' being` disposed*Y between the confrontingl surfacesof'the other of saidpairs off'insulators, at least one insulator of eachfof said 'pairs having av series v'of spacedportions extending'therefrom toward its companion insulator, respectively,

'said extending- Aportions overlapping adjacent :re-

exed portions, respectively, of saidfelementfor retainingcsa-id reflexedfportions Aagainst' movement lin aA direction inwardlyxof' :said fadiacent ireflexed portions, land; means: for holdingpsaid'in `su-lators in- 'said' positions thereof.

2; A resistor vcomprising a `resistance element 'havingra Seriesof reflexed portionsV along the length thereoif'at iits opposite .longitudinal sides,

a plurality `of pairswoffinsulators for mounting said resistance element, the :companion linsu- Vlatorsffof one orsaid pairs-noi insulators being -ipo'sitioned' :inropposed' confronting relation, the re'iexedwpontions oi-isad'nlement at oneeofisad having a4 series of reflexed portions` along` the .lengt-h thereof at' its vopposite longitudinalA sides,

'afplurality yof pairs vof insulators formounting said resistance element, the companion insulaters of one of said ypairs of insulatorsfbeing positioned in opposed confronting relation, the confrontingf'surfaces, respectively, of saidacom- `panion yinsulators being contiguous to the Yre- *ileXed' portions of said element zat oneV of said 'longitudinal sides thereof and the companion insulators of kanother of said pairs of insulators being positioned in opposedV relation, the confrontingsurfaces, respectively, of said other-pair of insulators being contiguous to the relexed portions of said element at the opposite longitudinal side thereof, at least one insulator of each of said pairs having means projecting therefrom toward its opposing insulator, respectively, said rneans overlapping adjacent reiiexed portions, respectively, of said element inwardly of saidre'zfiexed portions, respectively, spacing members between the confronting surfaces `of the insulators of each pairfor preventingV movement of thecornpanion insulators toward each other and providing clearance between the resistance element and the insulators, said insulators `havinglongitudinal grooves therein, respectively, .and means engaging said insulators for, l'ioldingsaidv insulators in the aforementioned positions thereof.

el.. Ay resistor, comprising a resistance element having, a series. of .refiexed portions along the .length thereof at its opposite longitudinal sides, apluralityofgpairs of insulatcrsfor mounting said .resistance element, the companion insullators of one of said pairs oiY insulators Vbeing .positioned inopposed cQDrontingl relation, the .confronting surfaces, respectively, of said corn- .panion insulators being contiguous to the re'- Aflexedportions of said element atene or said longitudinal sides t-hermfy and thecoinpanion insulatorsof anotheroi said pairs, oi insulators beingpositioned in opposed relation, theconfronting surfaces, respectively,k ofr said other pair of. .insulators.beingY contiguousto the re- `iexed.portions Ofsaid element at the opposite longitudinal side thereof, each 4.otsaid insu- .l-ators .having a.. series .01. .spaced portions projecting therefrom toward its coinpanionninsu- .lettone-,respectively s,aid..projectingportions overlapping adjacent, reexed, portions,V respetively, of-.saidelement-,attrae inner sides of saidportions, Nrespectively., .spacing members between theeV confronting. surfaces of the insulator-s .of

leach pair v.for Ypreventing movementof the .companiondnsulators. toward: each .other .and-provid-ing clearance- Ybetweenl thev resistance f element and ins-*insulators en@ means @essaies insulators for holding said insulators in the aforementioned positions thereof.

5. A resistor` comprising a resistance element having a series of reiiexed portions along the length thereof at its opposite longitudinal sides, a plurality of pairs of insulators for mounting said resistance element, the companion insulators of one of said pairs of insulators being positioned in opposed confronting relation, the reflexed portions of said element at one of said Vlongitudinal sides thereof being engaged between the confronting surfaces of said one pair of insulators and the companion insulators of another of said pairs of insulators being positioned in opposed relation, the reflexed portions of 4said element at the opposite longitudinal side Ythereof being engaged between t-he confronting surfaces of the other of said pairs of insulators, each of said insulators having a series of spaced projecting portions which overlap adjacent reflexed portions, respectively, of said element at the inner sides of said portions, respectively, the insulators of each pair being disposed so that the said spaced portions of one insulator of the pair project toward and are in registry with the spaced portions, respectively, of the other insulator of the pair.

6. A resistor comprising a resistance element having a series of reiiexed portions along the length thereof at its opposite longitudinal sides, a plurality of pairs of insulators for mounting said resistance element, the companion insulators of one of said pairs of insulators being positioned in opposed confronting relation, the reflexed portions of said element at one oi' said longitudinal sides thereof being disposed between the confronting surfaces of said one pair oi' insulators, the companion insulators of another of said pairs of insulators being positioned in opposed relation, the reilexed portions of said element at the opposite longitudinal side thereof being disposed between the confronting surfaces of the other of said pairs of insulators, each of said insulators having a series of spaced portions projecting therefrom toward the companion insulator, respectively, said projecting portions overlapping adjacent reflexed portions, respectively, of said element at the inner sides of said reiiexed portions, respectively, each of said insulators having spaced transverse grooves in the spaces between said spaced portions, respectively, the grooves of one insulator of a pair being in opposed confronting relation with the grooves of the other insulator of the pair, a terminal member disposed in a selected pair of confronting grooves of a pair of opposed insulators at one longitudinal side of the resistance element and supported by said pair of insulators, and a terminal member similarly disposed and supported by a pair of insulators at vlongitudinal sides thereof being disposed between the confronting surfaces of' said one pair of insulators, the companion insulators of another oi said pairs of insulators being positioned in opposed relation, the reilexed portions of said element at the opposite longitudinal side thereof being disposed between the confronting surfaces of the other of said pairs of insulators, at least one insulator of each of said pairs having a series of spaced portions extending therefrom toward its companion insulator, respectively, said extending portions overlapping adjacent reexed portions, respectively, of said element for retaining said reilexed portions against movement in a direction inwardly of said adjacent reilexed portions, a terminal member extending transversely of the confronting surfaces and between said confronting surfaces of the opposed insulators of a, pair at one side of said resistance element, a terminal member extending transversely of the confronting surfaces and between said confronting surfaces of the opposed insulators of a pair at the opposite side of said element, said terminal members being supported by said insulator pairs, respectively, and connected to each other and to a part of said resistance element in the space between the said two last mentioned pairs of insulators.

8. A resistor comprising a resistance element having a series of reflexed portions along the length thereof at its opposite longitudinal sides, a plurality of pairs of insulators for mounting said resistance element, the companion insulators of one of said pairs of insulators being positioned in opposed confronting relation, the reflexed portions of said element at one of said longitudinal sides thereof being disposed between the confronting surfaces of said one pair of insulators, the companion insulators of another of said pairs of insulators being positioned in opposed relation, the reflexed portions of said element at the opposite longitudinal side thereof being disposed between the confronting surfaces of the other of said pairs of insulators, at least one insulator of each of said pairs having a series of spaced portions extending therefrom toward its companion insulator, respectively, said extending portions overlapping adjacent reflexed portions, respectively, of said element for retaining said reflexed portions against movement in a direction inwardly of said adjacent reflexed portions, a terminal member extending transversely of the confronting surfaces and between said confronting surfaces of the opposed insulators of a pair at one side of said resistance element, a terminal member extending transversely of the confronting surfaces and between said confronting surfaces of the opposed insulators of a pair at the opposite side of said element, said terminal members being supported by said insulator pairs, respectively, and connected to each other and to a part of said resistance element in the space between said two last mentioned pairs of insulators, said terminal members having inner end portions extending transversely of said part of the resistance element, said end portions being secured to each other, said terminal members having outer portions which are in angular relation to their said inner end portions, respectively, each of said outer end portions having an opening for a terminal fastener.

9. A resistor, comprising a resistance element which includes a plurality of transverse parts connected to each other by end portions dis- -and;fthesencl portions atltheaoppositegside off sai 9a posed :inspected:relation at'. eeeh: et the :10,121,191 site longitudinal sidesspflthe element, and pairs.. of opposed` ,insulatorserat peach of `said opposite longitudinal; sides dispos/edili spaced confront-Vt element beingdisposed betweeattle seni @ming-l SurfacesJ of.; theinsulators e or4`- another pa1 least one insulator of each of said pairsvlaai/i7.TV

ing1 .a .plurality .of spaced :means proiettate these.-

frOm-Ltoward thelopppsinsinsulater, Vr entirely: said .projecting orerlappngedieeep enfiJ portionsgrespectively, ofwsaid element for` tainingsadeend portionspgainst moi/.em t. a

a directio n,inwardly of said end ,portions 105./x Apresistonlcomprising, aresistance ciernentv which. includes. 4a plurality, of; transverselparts connected to eacl1,otl1e1'.-.byendportionsdisf posedsinspacedrelationat each or theoppoe sitetlongitudinal sides .of fthe.,.element, and pairs oflA opposed .insulators atY each, of said.. opposite longitudinal sides. disposed .in spaced comrolit-vv ing .relationandenga'ging: theend portions. only n ment ofas'aidplementlat said oppositesides, respecrj 00..

tively, ofvisaid element...for. supporting thelate. teronly at saidiopposte longitudinal sidesA thereosthe end .portionsfatone side ofthe re-y sistance element-being positioned-betweenl the l confronting'A surfaces -orethe insulators of.A one of-said pairs and the endiportions a't the oppo,` site side "of said-element being disposed. between the'confroriting surfaces ofthe insulatorsof an: other pair atl least.A one insulator of .each of saidpair's "having plurality of.. spaced. means projecting` therefrom towardl tlie opposing ine` sulator, lrespectivelyY said projecting4` means overlapping adjacent fendsportions, respectively, of said `ele'rrl'ent for retariingsaidendportions, ag'ai'isv't`l movement inv a .direction inwardly of said i lend portions, av terminal member extend: in'g transversely of the confronting surfaces andIv between said confronting surfaces .of the opposed `insulators dita pair.-at .onesideofssaidrer V 5 sistance element, .a terminal` member extending transversely oft the confrontingv surfaces ,andg between saidconfronting .surfaces l of, the op; posedoinsulators oifaepairv at thelopprsite, side of.said element, said y terminal.. members.. being 55 supported by said .insulaton pairs', respectively, andconnected. to eachother ,andto oneV ofgtiic.k said transverse part-s. of said I resistance element.

1'1. Af resistor, compr'singa resistance element which includes a plurality ottransverse parte connected.- .toleach other by .end portions disposed .in spaced relation ateach ofthe opposite longitudinaLsdesof theuelement, andA pairs of opposedinsulators-.at each, of said. oppositek lon.;- a

gitudinal sides. Vdisposed* Y inv spaced .confronting `fronting surfaces.` of, the insulators... or anotherr` 75 pair,at leastonelinsulatorof each of `said pairs havingy aA p uralityoil spaced means projecting therefrornV otvarfd the opposing insulator,Y re.-

spe*ctiyely-vvY saidfp'rojectin'g "means voverlapping s adlacenl Lend.' portions, respectivelyyof said ele. V air'ii'ng said;y end` ,portions against r a; direction" inwardly of 'said end .insulators having longitudinalj for. ret mQXefeIlet? 1 ereeres, the?.

12E-Asesinos Gemert-sine e plurality of resister units disposed inna4v afferit` relation), eachre' sihstorn`A unitVLA comprising a"`resista`nce element which lxincludes* fa s plurality ,of transverse parts connected tofeach'otheii by end'fportions dise' posed in spaced relation at each" of. the ODDOSi't'e longitud rialsidesiofftlie element, "and pairs f`; opposed nsulato'rs all each vof said OllPOSitlon-j" gitudi'nal. sides' disposed in.V spaced confronting g the end .portions only of positsides; respectively,"

kl. .eedeseem seid elle Wentalt said. .16p of lsai^d element io'rfsup yortingtlie latter only' en v, mentfb 4ng p osi oliedbetwee surfacesj'of lith and theendportionsfat' thek oppositeside of said.` el e`ment"`being" disposed s between 'the' j conek 'surfaces 'of the' insulatorsf'of another K t eas'torelinsulator ofiea'chof said pairs;

n 'the confronting i"gxiooves"respectively lfor holding n chl other fbyy endfportionsdisposed in spaced relatmn at each -oLthe `opposite v longitudinal sides of the; lement,A fand "airsoft opposed insulatorsat' cacho said" opposite'flongitudinal sides disposed ingsp ed confronting relatinand engagingth'e end port'on'slonlyof said elemental: said opposite siseseresieetrely 1f-Seid element fer supporting" the latter only; at'saidlopposite longitudinal sides' thereoifthe end portions'at oneside of the resiste" epee elelent tetris pos'itierled' tetweet1 the e011-r fronting acesl of` the insulators offo'ne'iof said pairs andthe end pqrtionsfat the opposite si Oisaidelement being disposedbetyveen the co fronting Isurfac'es'of the insulators of another pair, at vleest, epe estlleter'e'teet ef. seid' seits having.. s a plurality, of4 spaced means' 'projecting therefrom toward the opposing insulator, respectively, said; projecting means overla'ppi'ng"adjacent end.: porjgaiyris,Y respectively, of's'aid" lelement fol-rctainingusaid end portions against move-A mem. in. e direction inwardly oi said, endl 'porltions, said insulators having longitudinal grooves therein. respectively, andi means. ,including longatsaid e pq'site'xiengimeinnsides thereof, the' ne'l'sid ,'offthe 'resistance ele-'-v risulators ojf"one"of saidv pairs a' plrlity ofi spaced" meansY projecting le therefrom toward the opposing insulator, 1regy nsulators inthe 'aforementioned lpositions'V l fcertain 'of v`said' longitudinal membersV d risinghajresistance element which; includes a plurality of 'transverse parts connected il gitudinal members engaging said insulators in said grooves, respectively, for holding said insulators in the aforementioned positions thereof, certain of said longitudinal members being common to and engaging the adjacent insulators of adjacent resistor units, and means for releasably securing said bars in spaced relation for holdf ing said insulators in said positions thereof.

14. A resistor, comprising a resistance element which includes a plurality of transverse parts connected to each other by end portions disposed in spaced relation at each of the opposite longitudinal sides of the element, and pairs of opposed insulators at each of said opposite longitudinal sides disposed in spaced confronting relation and engaging the end portions only of said element at said opposite sides, respectively, of said element for support-ing the latter only at said opposite longitudinal sides thereof, the end portions at one side of the resistance element being engaged between the confronting surfaces of the insulators of one of said pairs and the end portions at the opposite side of said element being engaged between the confronting surfaces of the insulators of another pair, at least one insulator of each of said pairs having means projecting therefrom toward its opposing insulator, respectively, said means overlapping adjacent end portions, respectively, of said element inwardly of said end portions, respectively, and spacing members between the confronting sides of the insulators of each pair for preventing movement of the companion insulators toward each other and providing clearance between the resistance element and the insulators.

15. A resistor, comprising a resistance element which includes a plurality of transverse parts connected to each other by end portions disposed in spaced relation at each of the opposite longitudinal sides of the element, and pairs of opposed insulators at each of said opposite longitudinal sides disposed in spaced confronting relation and engaging the end portions only of said element at said opposite sides, respectively, of said element for supporting the latter only at said opposite longitudinal sides thereof, the end portions at one side of the resistance element being en gaged between the confronting surfaces of the insulators of one of said pairs and the end portions at the opposite side of said element being engaged between the confronting surfaces of the insulators of another pair, at least one insulator of each of said pairs having means projecting therefrom toward its opposing insulator, respectively, said means overlapping adjacent end portions, respectively, of said element inwardly of said end portions, respectively, spacing members between the confronting sides of the insulators of each pair for preventing movement of the companion insulators toward each other and providing clearance between the resistance element and the insulators, and means engaging said insulators for preventing movement of the companion insulators away from each other and for preventing relative movement between the insulators at one longitudinal side of the resistance element and the insulators at the opposite longitudinal side of said element.

16. A resistor, comprising a resistance element which includes a plurality of transverse parts connected to each other by end portions disposed in spaced relation at each of the opposite longitudinal sides of the element, and pairs of opposed insulators at each of said opposite longitudinal sides disposed in spacedconfr'ntirig' relation and engaging the end portions only of said element at said opposite sides, respectively, of said element for supporting the latter only at said opposite longitudinal sides thereof, the end portions at one side of the resistance element being engaged between the confronting surfaces of the insulators of one of said pairs and the end portions at the opposite side of said element being engaged be tween the confronting surfaces of the insulators of another pair, each of said insulators having a series of spaced projections which are disposed transversely of said end portions, respectively, of the resistance element at their respective inner sides. Y

17. A resistor, comprising a resistance element which includes a plurality of transverse parts connected to each other by end portions disposed in spaced relation at each of the opposite longitudinal sides of the element, and pairs of opposed insulators at each of said opposite longitudinal sides disposed in spaced confronting relation and engaging the end portions only of said element at said opposite sides, respectively, of said element for supporting the latter only at said oprposite longitudinal sides thereof, the end portions at one side of the resistance element being engaged between the confronting surfaces of the insulators of one of said pairs and the end portions at the opposite side of said element being engaged between the confronting surfaces of the insulators of another pair, at least one insulator of each of said pairs having means projecting therefrom toward its opposing insulator, respectively, said means overlapping adjacent end portions, respectively, of said element inwardlyv of said end portions, respectively, there being a plurality of said pairs of insulators arranged in end to end relation at each of said longitudinal sides of the resistance element, said insulators having grooves therein in their outer sides, and holding bars received in the grooves of the insulators which are in said end to end relation, one barbeing common to a plurality of insulators.

18. An insulator comprising a block of insulation material having a series of spaced projections at one of two opposite sides thereof and a series of spaced transverse grooves in said side positioned in offset relation with respect to said projections transversely and longitudinally of the block, said projections having an axial dimension extending from a marginal edgeportion of said one opposite side to a point spaced from the opposing marginal edge portion of said one opposite side and said grooves extending from said opposing marginal edge portion to a point spaced from said first mentioned marginal edge portion.

19. An insulator comprising a block of insulation material having a series of spaced projections at one of two opposite sides thereof and a series of spaced transverse grooves in said side positioned in offset relation with respect to said projections transversely and longitudinally of the block, said projections having an axial dimension extending from a marginal edge portion of said one opposite side to a point spaced from the opposing marginal edge portion of said one opposite side and said grooves extendingfrorn said opposing marginal edge portion to a point spaced from said first mentioned marginal edge portion, and a longitudinal groove in the other of said two opposite sides of said block. f

20. An insulator comprising av block of insulation material having a series of spaced projec-f 13 tions at one of two opposite sides thereof and a series of spaced transverse grooves in said side positioned in offset relafion with respect to said projections transversely and longitudinally of the block, said projections having an axial dimension extending from a marginal edge portion of o 14 REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,706,014 Whittingham Mar. 19, 1929 s 1,883,927 Ipsen Oct. 25, 1932 1,900,318 Van Valkenburg et a1. Mar. 7, 1933 1,952,554 Lavarack Mar. 27, 1934 2,039,025 Papst i Apr, 28, 1936 2,202,874 Smalley June 4, 1940 2,256,727 Sloane Sept. 23, 1941 2,390,790 Immel Dec. 11, 1945 2,424,780 Trent July 29, 1947 

